1. Field of the Invention
This invention relates to an impeller blade for pumps which is particularly adapted for moving large quantities of heavy sediment in settling ponds.
2. Description of the Prior Art
Pumps for moving large volumes of waste water are generally of a centrifugal flow design. Centrifugal pumps move fluids by accelerating it radially outward. Centrifugal pumps consist basically of one or more rotating impellers in a stationary housing which guides the fluid from an inlet to an outlet location which is generally outward from the inlet. The rotating impeller imparts kinetic energy and pressure to the fluid being pumped, and the fluid pumped is in turbulent flow in the pump.
Impeller pumps have heretofore been used for pumping fluids from settling ponds and the like. Conventional impellers have been useful in pumping liquids and light sedimentary materials. It has heretofore been diffcult to pump heavy sediment, which contains little water, through centrifugal pumps because of the high viscosity of the sediment, the friction of the impeller blade through the sediment, and the need to operate the pump at a satisfactory speed to achieve an effective rate of flow.
The problems presented in pumping slurries and semi-solids such as sludge and sediment are increased when the material to be pumped includes a high volume of solids. In the case of a series of settling ponds, the last pond often has sediment which may be extremely thick and includes a large amount of debris such as weeds and trash of every conceivble variety. This material requires the pump impeller to rotate at a fairly low speed, with the result that heavy material tends to fall out of open inlet pumps. On the other hand, recessed impeller pumps must operate at lower heads and pressures on such heavy sediment and do not effectively force both the water and solids to the tip of the blade where the highest velocity is achieved.